Salt Deposits

Soil Salinity 012-10991 r1.04

Salt Deposits

Soil Salinity 012-10756 r1.04

The Snapshot button is used to capture the screen.

The Journal is where snapshots are stored and viewed.

The Share button is used to export or print your journal to turn in your work.

IntroductionJournals and Snapshots

Note: You may want to take asnapshot of the first page ofthis lab as a cover page for your journal.

Each page of this lab that contains the symbol

should be inserted into your journal. After completing a lab page with the snapshot symbol, tap (in the upper right hand corner) to insert the page into your journal.

Soil Salinity

Lab Challenge• How healthy is your soil?

• What is soil salinity?

• How does soil salinity impact the plants it supports?

• What causes changes in soil salinity?

Soil Salinity

Background• Soil salinity is a measurement of

the water-soluble salts present in soil.

• Salts are a widespread and natural component of all soils.

• However, an increase in salt concentration will adversely affect the growth of agricultural crops, decrease productivity, and threaten the balance of the earth's soil layer.

Soil Salinity

Self-check1. Soil containing any type of salt cannot support

plant growth.

a) true

b) false

Soil Salinity

...Background• The degree of crop damage and corrective action depends on the

concentration and type of salt accumulated. Soil that is high in soluble salts is referred to as saline soil.

Soil Salinity

...Background• As minerals in soils weather, they release salts. These salts are leached out of

the soil by ground or surface water in areas with sufficient precipitation.

• Salts are also deposited via dust and precipitation. In dry regions salts may accumulate, leading to naturally saline soils.

• The distribution of salt in soils is ultimately determined by the geology of the land. Ocean water can affect the salinity of soils in coastal regions.

Soil Salinity

Self-check2. How do different types of geologic terrain affect the salinity of surrounding soils?

Soil Salinity

...Background• Most of the salts present in irrigation

water contain magnesium, potassium, sulfates, and chlorides, in addition to sodium salts.

• Additionally, fertilizers contain many different kinds of salts, including nitrogen and calcium salts. Over-fertilizing and improper irrigation techniques aggravate pre-existing soil salinity conditions.

Soil Salinity

3. Explain how the contents of fertilizers can affect soil salinity.

Self-checkSoil Salinity

Safety• Follow all standard laboratory safety procedures.

• Wear safety glasses.

• Keep water away from sensitive electronic equipment.

• Wash your hands after handling soils.

Radiation Energy Transfer

Materials and EquipmentCollect all of these materials for your group.

Materials shared across the class.

• Conductivity sensor

• Digging tool

• Stirring rod

• Beaker, 100-mL (4)

• Plastic zip lock bag (3)

• Graduated cylinder, 100-mL

• Wash bottle containing deionized or distilled water

• Waste container

• Permanent marker

• Paper towels

Soil Salinity

The steps to the left are part of the procedure for this lab activity. They are not in the right order. Determine the correct sequence of the steps, then take a snapshot of this page.

Sequencing Challenge

A. Use the sensor to measure the conductivity of the soil sample.

B. Plug the conductivity sensor into your SPARK Science Learning System.

C. Identify the prevalent organisms and plant types at the collection site.

D. Crush a dry soil sample into a fine dust and mix with water.

Soil Salinity

Setup

1. Using the digging tool, gather 3 soil samples from different locations. If possible, find soils that differ in appearance, composition, and in the type of plants growing nearby.

2. Use the next three pages to record field notes about each of your soil samples.

Note: Give each sample a label, describe its appearance, and describe what kinds of plants are growing nearby.

3. Take a snapshot of each page of your field notes.

Soil Salinity

Soil Salinity

Soil Salinity

Soil Salinity

Setup4. Crush each of the soil samples into as fine a dust

as possible. Remove any rocks, sticks, etc.

5. Plug the conductivity sensor into your data collection system. The values from this sensor indicate the concentration of salts in a soil sample.

6. You may need to set the conductivity sensor to the appropriate sensitivity.

Soil Salinity

Self-CheckQ1: Why is it important to set the sensitivity of the conductivity sensor to suit

the sample you are testing?

Soil Salinity

Setup7. Label 3 of the beakers as "Sample 1," "Sample 2," and "Sample 3."

8. Add about 4 tablespoons of each of your soil samples into the corresponding labeled beaker.

9. Add about 4 tablespoons of distilled water into each beaker.

10.Mix the soil and water thoroughly in each beaker. Clean your stirring rod between each beaker to avoid cross-contamination.

11.Allow the muddy mixtures to sit for approximately 5 minutes.

Soil Salinity

Procedure1. Rinse the conductivity sensor with distilled water,

then slowly swirl it in the Soil 1 solution.

2. Tap to activate the sensor display.

3. Once the conductivity value stabilizes, tap . If necessary, adjust the sensitivity of the sensor.

4. Record conductivity value in the box to the right.

5. Repeat steps 1-4 using Soil Samples 2 and 3. Always rinse the sensor between each trial.

Soil Salinity

Procedure6. Rinse the conductivity sensor with distilled water.

7. Pour 50 mL of distilled water into the fourth beaker. Then place the sensor into the water.

8. Tap to activate the sensor display.

9. Once the conductivity value stabilizes, tap .

10. Record the conductivity value for the distilled water in the box to the right.

11. Take a snapshot of this page.

12. Save your work then follow your teacher’s instructions for cleaning up.

Soil Salinity

Analysis1. What factors (variables) did you attempt to control (keep the same) across all 3

trials?

Soil Salinity

Analysis2. What was the independent variable (the variable you chose to change)?

3. What was the dependent variable (the variable that changed under the different experimental conditions in the 3 trials)?

Soil Salinity

Analysis4. Why did you add water to the soil samples before testing them?

Soil Salinity

Analysis5. Which of the three soil solutions had the highest conductivity? Explain why it

might be higher than the other two samples. Recall information describing the location of the sample.

Soil Salinity

Analysis6. Which of the three soil solutions had the lowest conductivity? Explain why it

might be lower than the other two samples. Recall information describing the location of the sample.

Soil Salinity

Synthesis1. Why was distilled water tested? Why is this important in scientific research?

Soil Salinity

Synthesis2. What factors may have interfered with the accuracy of your

conductivity measurements?

Soil Salinity

Synthesis3. How would the results of the experiment change if the water and soil

mixtures were allowed to sit overnight prior to testing? Would the conductivity increase or decrease? Why?

Soil Salinity

Multiple Choice1. A salt is __________.

a) a solid that does not dissolve in water

b) a solid that dissolves in water, with the molecules remaining intact

c) a solid that dissolves in water, dissociating into positive and negative ions

d) a chemical that is highly toxic at very small concentrations

e) both C and D

f) None of the above.

Soil Salinity

Multiple Choice2. An ion is __________.

a) the smallest unit of matter

b) an element with a unique atomic number

c) an atom with a net electrical charge

d) an element having the same atomic number but a different mass number

e) another name for a positively charged subatomic particle

Soil Salinity

Multiple Choice3. Salinization refers to __________.

a) release of toxic metals such as Al, Fe, Mn, and Ni

b) deficiencies of micronutrients such as B, Fe, and Mn

c) release of calcium carbonate

d) increase in salts

e) None of the above.

Soil Salinity

You have completed the lab.Congratulations!

Please remember to follow your teacher's instructions for cleaning-up and submitting your lab.

Soil Salinity

All images were taken from PASCO documentation, public domain clip art, or Wikimedia Foundation Commons:

http://commons.wikimedia.org/wiki/File:Salinity.jpghttp://commons.wikimedia.org/wiki/File:Helianthus_annuus_exposed_2004-05-22.jpghttp://commons.wikimedia.org/wiki/File:Field,_corn,_Liechtenstein,_Mountains,_Alps,_Vaduz,_sky,_clouds,_landscape.jpghttp://commons.wikimedia.org/wiki/File:Forest_fertilizer.JPG http://commons.wikimedia.org/wiki/File:Soil_survey_1923.jpghttp://commons.wikimedia.org/wiki/File:Washbottles.JPGhttp://www.freeclipartnow.com/office/paper-shredder.jpg.html

ReferencesSoil Salinity